This invention relates to solenoid valve assemblies and more particularly to a clamp ring for releasably securing the electromagnetic coil assembly on the core tube of a solenoid valve.
Solenoid valve assemblies conventionally comprise a valve body having a fluid valve therein and an electromagnetic device for actuating the valve in response to an electric current. The electromagnetic device typically comprises a core tube assembly, including a fixed pole piece and a slidable plunger retained in a core tube, and an electromagnetic coil assembly surrounding the core tube to create magnetic flux and movement of the plunger. It is desirable to be able to mount different coil assemblies on the core tube both for replacement purposes and for selection purposes due to different power requirements for certain valves and applications and because of the different power sources in existence. It is also desirable, on a production line basis, to be able to rapidly and accurately assemble or interchange coil assemblies on various valve structures, both of which may be slightly different in size due to manufacturing tolerances and the like.
It has become common to construct the electromagnetic coil assembly as a unit which can be removed for entire replacement or for replacement of component parts thereof and to facilitate high production assembly thereof. Typically, a clip or similar clamping device is employed which engages a groove formed in an outer part of a core tube or the fixed pole piece to secure the coil assembly on the core tube. A spring clip may be used to retain the clip in position and also to create a bias urging the coil assembly against the valve body. This form of assembly provides a device for resiliently mounting the coil assembly and for accommodating the stack up of tolerances of the various component parts.
One such prior art example of spring clip for a solenoid valve is described in U.S. Pat. No. 3,295,079 wherein a dome shaped clip having a central u-shaped yoke is retained in a groove at the outer end of a fixed pole piece, with the periphery of the clip in engagement with the upper surface of the solenoid coil assembly. No circumferential adjustment of the spring clip is possible with this device.
Another prior art example is disclosed in U.S. Pat. No. 3,281,740 wherein a plastic cap is snapped over an integral split collar to secure the latter in a groove of the core tube. This type of clamp relies on the resilient nature of the plastic material to yieldably accommodate dimensional variations of the core tube and housing, but is limited in this regard and typically requires separate spring washers and the like to achieve this function. Further, this type of device is essentially a two-part device joined by a connector strap and is subject to breakage due to the severe bending requirement. Further, it can only be applied at the end of a shaft and requires a difficult to mold undercut in its cap configuration.
A similar prior art example is shown in U.S. Pat. No. 3,727,160 wherein a spring clip is adapted to be slipped over the end of the core tube and retained by an overlying spring arm. The clip is shown in horseshoe and closed end configurations, but provides no circumferential adjustment feature.
Other prior art devices are disclosed in U.S. Pat. Nos. 3,818,398 and 4,055,823, both of which utilize a threaded securing member fastened over the end of a shaft. The former is simply a threaded nut while the latter is a two part device telescopically threaded to interengage with the housing of a coil assembly and a groove in the core tube.
Many versions of plastic clamp having interengaging teeth are known in the prior art. One such variation is described in U.S. Pat. No. 3,925,851. However, these are designed primarily for encirclement and clamping of an object such as a hose and none is known which is particularly suited for electromagnetic coil assembly applications in which an axial bias force is also desired.